1. Field of the Invention
The present invention relates to an image management apparatus and method, image management system, and storage medium for accumulating image data having a hierarchical structure.
2. Related Background Art
Most of conventional image services of this type provide search images (index images) as service images.
Recent photo-CDs use an image format having a multi-level hierarchical structure in which the image length and width are set to xc2xd, xc2xc, xe2x85x9, . . . and the area is set to xc2xc, {fraction (1/16)}, {fraction (1/64)}, . . . .
An example of image database design devices having this hierarchy image format is one having a low-speed large-capacity external storage device (CD-ROM changer or the like) and a high-speed small-capacity external storage means (cache hard disk and the like).
Algorithms for the cache of the high-speed small-capacity external storage means are
(1) a method of storing only reduced images in the high-speed small-capacity external storage device,
(2) a method of storing all images requested once for retrieval in the high-speed small-capacity external storage device, and
(3) a method of erasing and replacing images in the order from older access dates.
As for the server configuration method, a xe2x80x9cforgetful image databasexe2x80x9d is proposed.
For example, xe2x80x9cImage Database System With Graceful Oblivision Mechanism and Three-Dimensional Browserxe2x80x9d, Journal of the Institute of Image Electronics Engineers of Japan, Vol. 25, No. 4, pp. 339-350, 1996 reports that the coefficient of popularity is defined, and hierarchy images are erased and replaced in the order from smaller coefficients, thereby increasing the cache hit ratio.
In such systems, if requested images are not stored in the high-speed small-capacity external storage means (cache hard disk or the like), the user""s waiting time becomes long, and no good services can be provided.
For this reason, images left in the high-speed small-capacity memory means determine the effectiveness of the system.
That is, the cache hit ratio on a hierarchy corresponding to an image requested by the user must be increased to shorten the user""s average waiting time.
According to an aspect of the present invention, there is provided an image management apparatus which retrieves image data having a hierarchical structure from low-speed large-capacity storage means to high-speed small-capacity storage means to provide desired image data, comprising first judgment means for judging a free volume of the small-capacity storage means, and control means for, when the first judgment means judges that the small-capacity storage means does not have a free volume, erasing image data of a hierarchy having a large volume from the image data stored in the small-capacity storage means.